Active vibration control systems have been employed to control vehicle seat vibration. For example, as a replacement for passive systems including springs and dampers which reduce seat response to vehicle vibration, active vibration control systems detect seat vibration and control the position of the seat to cancel detected motion and thereby isolate the seat from vehicle vibration. Such active vibration control systems may include a linear actuator controlled by a controller. The linear actuator is positioned below the seat to control seat position relative to the vehicle frame. For example, the linear actuator may include a linear electromagnetic motor, including an armature fixed at one end to the seat. The armature linearly extends and retracts relative to a stator based on control signals from the controller, thereby positioning the seat.
Controlled linear actuators have application to systems other than vehicle seat vibration control. For example, controlled linear actuators are also known to be used in vehicle wheel suspension systems and in engine valve control systems.
In many applications, a challenge associated with using such linear actuators to control object position includes providing a linear motor providing sufficient linear travel within a limited space, for example between the seat and the floor in an active seat vibration control system. Other challenges include known cost and maintenance issues associated with linear motors.